1. Field of the Invention
This invention relates to a control device for vehicular automatic transmission to execute a backpressure control to control a backpressure of accumulators while executing a torque-up control for raising output torque of a drive force source. More particularly, it relates to a technology of suppressing the occurrence of interference between learning on such controls.
2. Description of the Related Art
There has heretofore been known a vehicular automatic transmission having hydraulically operated frictional engaging devices whose engaging states are controlled with a hydraulic pressure, and accumulators (pressure accumulators) for controlling the hydraulic pressure being supplied to the hydraulically operated frictional engaging devices. With such an automatic transmission, a gearshift operation is executed during which a backpressure of the accumulators is controlled for controlling the engaging states of the hydraulically operated frictional engaging devices depending the associated backpressure. It has been often difficult to estimate actual engaging pressures of the hydraulically operated frictional engaging devices depending on the backpressure of the accumulators.
With such an automatic transmission, there has been known a technology of effectuating a torque-up control for minimizing pull-in of a torque phase occurring during the gearshift operation. For instance, such a technology is disclosed in Patent Publication 1 (Japanese Patent Application Publication No. 2001-214771) related to a throttle control device for internal combustion engine.
With such a technology, torque phase detecting means actually detects a beginning time and an ending time of a torque phase during a shift-up mode for controlling a throttle valve opening so as to increase torque, output from a drive-force source, in the presence of the torque phase. This control is executed based on the beginning time and ending time of the torque phase detected by the torque phase detecting means. This accurately results in coincidence between a period in which torque output from the drive-force source increases, and a period in which the torque phase is generated, appropriately enabling the suppression of a shifting shock encountered in the shift-up mode.
Another technique disclosed in the Patent Publication 2 (Japanese Patent Application Publication No. 10-331962) and the Patent Publication 3 (Japanese Patent Application Publication No. 2004-257197) has been known.
In order to appropriately execute the torque-up control set forth above, meanwhile, a need arises for performing learning on timing at which the torque-up control is commenced, and learning on the backpressure of accumulators in the presence of a gearshift operation. However, with such a technology of the related art, defect of a difficulty of appropriately performing a learning step may occur due to interference between the steps of learning simultaneously executed. Therefore, research and development work has been required to provide a control device for a vehicular automatic transmission that can cancel interference between learning on the backpressure of the accumulators and leaning on the torque-up control during the gearshift operation.